diff --git a/change_quality.py b/change_quality.py
index b5fc4a4..15562d8 100644
--- a/change_quality.py
+++ b/change_quality.py
@@ -61,7 +61,7 @@ def generate_quality_next_bases_rv(read_length):
     return ''.join(random.choice('ABCDEG') for _ in range(int(read_length * 0.02)))
 
 def generate_quality_middle_bases_rv(read_length):
-    return ''.join(random.choice('CDEFGH') for _ in range(int(read_length * 0.02)))
+    return ''.join(random.choice('EFGH') for _ in range(int(read_length * 0.02)))
 
 def generate_quality_main_bases_rv(read_length):
     return ''.join(random.choice('HI') for _ in range((int(read_length * 0.10) * 6) + (int(read_length * 0.05))))